What determines the power level of a power an ardent can pick?

Question

The standard class ardent (Complete Psionic 5-8) on Powers Known, in part, says

At each additional level, an ardent learns one new power from her available mantles. She must be able to manifest the new power at the level at which she learns it, however. For example, an ardent who attains 5th level can learn any power from one of her mantles that costs 5 power points or less to manifest; she cannot learn a power from a mantle that costs more than 5 power points to manifest until she attains a level capable of manifesting a power with that cost. (7)

(Emphasis mine.) How is this able to manifest determined? For example, are what powers an ardent can pick based on the power point bottleneck—i.e. "you can't spend more power points on a power than your manifester level" (Expanded Psionics Handbook 54), a statement that so far as I can tell is absent from the Complete Psionic—; on the number of raw power points the ardent possesses when the creature gains an additional level of ardent; or on something else entirely that I've overlooked?

Answer 1

The limiting factor on the maximum level of power an Ardent can learn is, as speculated in the question and correctly pointed out in Ben Barden's answer, the limit on the number of power points a manifester can spend on a single power. From XPH (and the SRD):

you can’t spend more power points on a power than your manifester level

Your manifester level is specific to each psionic class, just like caster level. From the SRD:

The variables of a power’s effect often depend on its manifester level, which is equal to your psionic class level.

However, it's important to note that manifester level is not the same thing as Ardent level. Your manifester level (and thereby the number of power points you can spend on a single power) can be increased by things like:

• The Practiced Manifester feat (CPsi), which provides +4 ML to a maximum of your total HD
• Arguably the Overchannel feat, though some DMs may rule that Overchannel applies only at the time of manifesting and therefore doesn't factor into the maximum level of power you can manifest
• Depending on your DM's rulings on Magic/Psionics transparency (and potentially also the Ardent's Magic mantle), anything that increases caster level, such as an orange ioun stone or a bead of karma
• Bloodlines

This means that Ardents (especially multiclass Ardents, who can get +4 ML, no questions asked, for the bargain price of a single feat) can potentially learn high-level powers with an investment of relatively few class levels. For instance, an Ardent 1/Barbarian 3 with the Practiced Manifester feat could take their second level of Ardent at level 5 (becoming an Ardent 2/Barbarian 3) and learn a third level power.

According to Nijineko in the comments, and corroborated in an old forum thread, the author of the class is apparently on record as saying there were intended to be stricter limits to the maximum level of Ardent powers known. As far as I can tell, though, this never made it into any official rules source like an errata document, or even a quasi-official source like an FAQ. I am unable to find the original comment at all; it may have been lost in one of the WotC forum purges.

The balance implications of this situation, and any authorially-approved houserules to correct it, are left as an exercise for the reader and/or a conversation to have with your DM.

Answer 2

It's the power point bottleneck. It doesn't matter how many points you have in the tank. If you can't spend enough points on a single power to meet the minimum necessary to manifest that power, you can't manifest that power.

This also matches up with the pattern of minimum cost to manifest and minimum levels necessary to learn high-level powers for classes like the psion.

It also matches up pretty directly with the example quote you have there. 5th level means you can spend 5 power points. That means you can learn anything that costs 5 power points or less to manifest.

Complete Psionic is supplemental to the Expanded Psionics Handbook.